Traditional Chinese medicines (TCMs) are gaining increasing popularity throughout the world due to their long historical clinical practices. Highly efficient analytical separation tools are essential for ... [more ▼]

Traditional Chinese medicines (TCMs) are gaining increasing popularity throughout the world due to their long historical clinical practices. Highly efficient analytical separation tools are essential for investigating the mysterious properties of TCMs and their quality control. Supercritical fluid chromatography (SFC) showed a great potential in TCM analysis for both nonpolar and polar components. In this paper, an overview of the experimental conditions (i.e. detection mode, stationary phase, mobile phase composition, pressure and temperature) used in SFC for achiral separations of TCM components is presented and recent applications to the analysis of different classes of compounds extracted from TCMs, such as lipids, terpene and terpenoids, phenolic compounds, flavonoids, alkaloids, saponins and carbohydrates, will be briefly described. [less ▲]

Tea (Camellia sinensis L.) is a complex mixture containing a wide range of biological activities and has been used as widely consumed beverages and natural medicine for over thousand years [1-2]. In this ... [more ▼]

Tea (Camellia sinensis L.) is a complex mixture containing a wide range of biological activities and has been used as widely consumed beverages and natural medicine for over thousand years [1-2]. In this study, a novel method for high-performance liquid chromatography with mass spectrometry (SFC-MS) has been developed to simultaneously determine the contents of 11 free amino acids in different types of teas (pu-erh tea, green tea, black tea and oolong tea). The separation conditions for the selected amino acids were carefully optimized such as the column type, temperature and backpressure, the type of additive. The best compromise for tested analytes in terms of chromatographic performance was obtained when water (5%) and trifluoroacetate acid (0.4%) were added to the supercritical carbon dioxide/methanol mobile phase. Finally, the developed SFC-MS method was successfully applied to the analysis of the 11 amino acids present in the teas and fully validated as well. The results indicated a good linearity (r ≥0.995), precision (RSD≤ 2.99%), stability (RSD≤ 2.88%) and accuracy (91.95%~107.99%). The limits of detection ranged from 1.42 to 14.69 ng/mL, respectively, while the limits of quantification were between 4.53 and 47.0 ng/mL. The content of the amino acids in six different tea samples were also determined and presented some difference basing on the fermentation processes. The proposed SFC-MS method showed a great potential in further investigations to differentiate tea varieties [less ▲]

The discovery of lead compounds that can modulate the activity of a biological target is essential to provide efficient pharmacological tools and to serve as starting points for new drug generations ... [more ▼]

The discovery of lead compounds that can modulate the activity of a biological target is essential to provide efficient pharmacological tools and to serve as starting points for new drug generations. Fragment-based drug discovery (FBDD) approach is an attractive tool for the identification of new selective inhibitors of a target of interest, but its success largely depends on the ability to develop screening bioassays capable to detect and gauge weak affinity binders. To achieve this goal, we investigated capillary electrophoresis (CE) for identifying and ranking fragments from an initial library. Indeed, due to its ability to evaluate weak interactions, CE seems to be promising for fragment-based screening. This technique is a powerful analytical tool with a unique separation mechanism, speed, efficiency and versatility. Its main advantages are low protein consumption, higher throughput compared to NMR and X-ray crystallography and the fact that screening can be carried out using native protein in physiological solution without the need of immobilization. We developed a proof of concept study on thrombin, a serine protease implicated in the coagulation cascade using affinity capillary electrophoresis (ACE) for ranking fragments from an initial library. For this study, we followed a probe ligand, benzamidine, and we investigated interactions with the target by monitoring the changes of its electrophoretic mobility upon binding. The first step of this study consisted in the optimization of the experimental conditions suitable for the CE method (target and probe ligand concentrations, separation buffer composition, voltage, separation effective length, target partial filling…). Then, numerous thrombin inhibitors with a wide range of inhibitory potency (i.e. Ki 200 µM – 5 nM) were tested to validate our system demonstrating the possibility to fish binders in the optimized conditions. We also checked the absence of non-specific binding with the target using the inactivated enzyme at the binding site. It is noteworthy that in this operating system (ACE assay), binding occurs in free solution using physiological buffers, thus preventing artifacts that may result from target immobilization, which is a requirement for some techniques such as SPR. [less ▲]

The discovery of lead compounds that can modulate the activity of a biological target is essential to provide efficient pharmacological tools and to serve as starting points for new drug generations ... [more ▼]

The discovery of lead compounds that can modulate the activity of a biological target is essential to provide efficient pharmacological tools and to serve as starting points for new drug generations. Fragment-based drug discovery (FBDD) approach is an attractive tool for the identification of new selective inhibitors of a target of interest, but its success largely depends on the ability to develop screening bioassays capable to detect and gauge weak affinity binders. To achieve this goal, we investigated capillary electrophoresis (CE) for identifying and ranking fragments from an initial library. Indeed, due to its ability to evaluate weak interactions, CE seems to be promising for fragment-based screening. This technique is a powerful analytical tool with a unique separation mechanism, speed, efficiency and versatility. Its main advantages are low protein consumption, higher throughput compared to NMR and X-ray crystallography and the fact that screening can be carried out using native protein in physiological solution without the need of immobilization. We developed a proof of concept study on thrombin, a serine protease implicated in the coagulation cascade using affinity capillary electrophoresis (ACE) for ranking fragments from an initial library. For this study, we followed a probe ligand, benzamidine, and we investigated interactions with the target by monitoring the changes of its electrophoretic mobility upon binding. The first step of this study consisted in the optimization of the experimental conditions suitable for the CE method (target and probe ligand concentrations, separation buffer composition, voltage, separation effective length, target partial filling…). Then, numerous thrombin inhibitors with a wide range of inhibitory potency (i.e. Ki 200 µM – 5 nM) were tested to validate our system demonstrating the possibility to fish binders in the optimized conditions. We also checked the absence of non-specific binding with the target using the inactivated enzyme at the binding site. It is noteworthy that in this operating system (ACE assay), binding occurs in free solution using physiological buffers, thus preventing artifacts that may result from target immobilization, which is a requirement for some techniques such as SPR. [less ▲]

Flavonoids from plants always show a wide range of biological activities [1-2]. In the present study, a rapid and highly efficient supercritical fluid chromatography (SFC) method was developed for the ... [more ▼]

Flavonoids from plants always show a wide range of biological activities [1-2]. In the present study, a rapid and highly efficient supercritical fluid chromatography (SFC) method was developed for the separation of 12 flavonoids. After careful optimization, the 12 flavonoids were baseline separated on a ZORBAX RX-SIL column using gradient elution. A 0.1% phosphoric acid solution in methanol was found to be the most suitable polar mobile phase component for the separation of flavonoids. From the viewpoint of retention and resolution, a backpressure of 200 bar and a temperature of 40 °C were shown to give the best results. Compared with a previously developed reverse phase liquid chromatography method, the SFC method could provide flavonoid separations that were about three times faster, while maintaining good peak shape and comparable peak efficiency. This SFC method was validated and applied to the analysis of five flavonoids (kaempferol, luteolin, quercetin, luteoloside, buddleoside) present in Chrysanthemum morifolium Ramat. from different cultivars (Chuju, Gongju, Hangju, Boju). The results indicated a good repeatability and sensitivity for the quantification of the five analytes with RSDs for overall precision lower than 3%. The limits of detection ranged from 0.73 to 2.34 μg/mL, while the limits of quantification were between 2.19 and 5.86 μg/mL. The method showed that SFC could be employed as a useful tool for the quality assessment of Traditional Chinese medicines (TCMs) containing flavonoids as active components. [less ▲]

Some of the D-amino acids (D-Ser, D-Asp, D-Glu) have gained an increasing attention during the last decades, due to the discovery of their role as neurotransmitters and their implication in different ... [more ▼]

Some of the D-amino acids (D-Ser, D-Asp, D-Glu) have gained an increasing attention during the last decades, due to the discovery of their role as neurotransmitters and their implication in different neurological pathologies (Alzheimer’s disease, schizophrenia etc.). Nevertheless, their use as biomarkers is particularly relevant when correlated with the levels of other neurotransmitters. In order to develop a fast and efficient separation method widely accessible for the quantitation of these molecules, we used only common separation tools such as RP-18 stationary phases for reversed phase liquid chromatography (RP-LC) or bare fused capillaries for capillary zone electrophoresis (CZE). For achieving chiral resolution, a derivatization procedure was implemented. (-)-FLEC was the chiral derivatization agent of choice due to its fast and quantitative reaction with primary and secondary amines and the ability of performing in-capillary derivatization. Moreover, the derivatization process implies only a simple mix of the sample and reagent, at room temperature. The separation of the FLEC derivatives of several biologically relevant D- and L- amino acids (Asp, Glu, Ser, Tyr, Trp, Phe, His) together with certain neurotransmitter molecules have been optimized using CZE or RP-LC, chiral resolution being achievable for all amino acids of interest. By the CZE approach the running buffer’s pH turned out to be critical in achieving baseline separation of the targeted analytes. The derivatives of most amino acids could be separated using 60mM acetate buffer at pH 5, while for Asp derivatives the separation could be achieved only at pH 4. Being stronger bases, a third run at a more alkaline pH was needed for the separation of the remainder neurotransmitters. Moreover, the implemented in-capillary derivatization allows a fast and fully automated separation procedure. As for the RP-LC approach 50 mM acetate buffer in combination with an organic modifier (methanol, acetonitrile or tetrahydrofuran (THF)) was tested as mobile phase using gradient elution. Once again, the strong influence of pH on the resolution was observed. The organic modifier nature was of critical importance, where only THF enabled baseline resolution for all amino acid derivatives. [less ▲]

in Journal of Pharmaceutical and Biomedical Analysis (2017), 144(213), 219

Nucleobases, nucleosides and ginsenosides, which have a significant impact on the physiological activity of organisms, are reported to be the active components of ginseng, while they are less present in ... [more ▼]

Nucleobases, nucleosides and ginsenosides, which have a significant impact on the physiological activity of organisms, are reported to be the active components of ginseng, while they are less present in ginseng extracts. Few analytical methods have been developed so far to simultaneously analyze these three classes of compounds with different polarities present in ginseng extracts. In the present study, a simple and efficient analytical method was successfully developed for the simultaneous separation of 17 nucleobases, nucleosides and ginsenosides in ginseng extracts using supercritical fluid chromatography coupled with single quadrupole mass spectrometry (SFC-MS). The effect of various experimental factors on the separation performance, such as the column type, temperature and backpressure, the type of modifier and additive, and the concentration of make-up solvent were systematically investigated. Under the selected conditions, the developed method was successfully applied to the quality evaluation of 14 batches of ginseng extracts from different origins. The results obtained for the different batches indicate that this method could be employed for the quality assessment of ginseng extracts [less ▲]

Over the last 30years, (+/-)-1-(9-fluorenyl)ethyl chloroformate ((+/-)-FLEC) was used as a chiral derivatizing agent in various analytical applications involving a wide range of endogenous, pharmaceutical ... [more ▼]

Over the last 30years, (+/-)-1-(9-fluorenyl)ethyl chloroformate ((+/-)-FLEC) was used as a chiral derivatizing agent in various analytical applications involving a wide range of endogenous, pharmaceutical and environmentally relevant molecules. This comprehensive review aims to present all the significant aspects related to the state of the art in FLEC labeling and subsequent chiral separation of the resulting diastereomers using LC, SFC and CE techniques. [less ▲]

Nucleobases, nucleosides and ginsenosides, which have a significant impact on the physiological activity of organisms, are reported to be the active components of ginseng, while they are less present in ... [more ▼]

Nucleobases, nucleosides and ginsenosides, which have a significant impact on the physiological activity of organisms, are reported to be the active components of ginseng, while they are less present in ginseng extracts. Few analytical methods have been developed so far to simultaneously analyze these three classes of compounds with different polarities present in ginseng extracts. In the present study, a simple and efficient analytical method was successfully developed for the simultaneous separation of 17 nucleobases, nucleosides and ginsenosides in ginseng extracts using supercritical fluid chromatography coupled with single quadrupole mass spectrometry (SFC-MS). The effect of various experimental factors on the separation performance, such as the column type, temperature and backpressure, the type of modifier and additive, and the concentration of make-up solvent were systematically investigated. Under the selected conditions, the developed method was successfully applied to the quality evaluation of 14 batches of ginseng extracts from different origins. The results obtained for the different batches indicate that this method could be employed for the quality assessment of ginseng extracts. [less ▲]

Flavonoids from plants always show a wide range of biological activities. In the present study, a rapid and highly efficient supercritical fluid chromatography (SFC) method was developed for the ... [more ▼]

Flavonoids from plants always show a wide range of biological activities. In the present study, a rapid and highly efficient supercritical fluid chromatography (SFC) method was developed for the separation of 12 flavonoids. After careful optimization, the 12 flavonoids were baseline separated on a ZORBAX RX-SIL column using gradient elution. A 0.1% phosphoric acid solution in methanol was found to be the most suitable polar mobile phase component for the separation of flavonoids. From the viewpoint of retention and resolution, a backpressure of 200bar and a temperature of 40 degrees C were shown to give the best results. Compared with a previously developed reverse phase liquid chromatography method, the SFC method could provide flavonoid separations that were about three times faster, while maintaining good peak shape and comparable peak efficiency. This SFC method was validated and applied to the analysis of five flavonoids (kaempferol, luteolin, quercetin, luteoloside, buddleoside) present in Chrysanthemum morifolium Ramat. from different cultivars (Chuju, Gongju, Hangju, Boju). The results indicated a good repeatability and sensitivity for the quantification of the five analytes with RSDs for overall precision lower than 3%. The limits of detection ranged from 0.73 to 2.34mug/mL, while the limits of quantification were between 2.19 and 5.86mug/mL. The method showed that SFC could be employed as a useful tool for the quality assessment of Traditional Chinese medicines (TCMs) containing flavonoids as active components. [less ▲]

Capillary Electrophoresis is a very efficient and resolutive separation technique used for many years in the analytical field. Despite all its assets, CE remains poorly used in drug discovery. This can be ... [more ▼]

Capillary Electrophoresis is a very efficient and resolutive separation technique used for many years in the analytical field. Despite all its assets, CE remains poorly used in drug discovery. This can be explained by the relatively low number of experienced CE practitioners, the maturity of HPLC in the pharmaceutical industry and some intrinsic limitations of the technique. The objective of this review is to focus our attention on recent developments of this technique in three different drug discovery areas: bioassays, drug-plasma interactions and drug metabolism studies. These developments were based on two important abilities of CE: the capacity to measure non-covalent interactions in solution and the ability to use a portion of the capillary as a reactor while the rest of the capillary is used for the separation of the product of the reaction. [less ▲]

The efficient separation and accurate determination of saccharides still remains a challenge due to the wide variety of possible isomers, high polarity, similar chemical composition and absence of ... [more ▼]

The efficient separation and accurate determination of saccharides still remains a challenge due to the wide variety of possible isomers, high polarity, similar chemical composition and absence of chromophores [1]. Supercritical fluid chromatography (SFC) is an attractive separation method often showing higher resolution and shorter analysis time compared to traditional GC and HPLC [2]. Few papers have reported on the SFC analysis of saccharides using standard compounds [3-4]. The aim of this study was to develop an efficient and sensitive method for the determination of fructose, glucose and sucrose in honey samples using SFC-MS. The method validation and application to the determination of these saccharides in different honey samples were also performed. [less ▲]

The sensitivity of coupled enantioselective capillary electrophoresis-mass spectrometry (CE-MS) of amino acids (AAs) is often hampered by the chiral selectors in the background electrolyte (BGE). A new ... [more ▼]

The sensitivity of coupled enantioselective capillary electrophoresis-mass spectrometry (CE-MS) of amino acids (AAs) is often hampered by the chiral selectors in the background electrolyte (BGE). A new method is presented in which the use of a chiral selector is circumvented by employing (+)-1-(9-fluorenyl)ethyl chloroformate (FLEC) as chiral AA derivatizing agent and ammonium perfluorooctanoate (APFO) as a volatile pseudostationary phase for separation of the formed diastereomers. Efficient AA derivatization with FLEC was completed within 10 min. Infusion experiments showed that the APFO concentration hardly affects the MS response of FLEC-AAs and presents significantly less ion suppression than equal concentrations of ammonium acetate. The effect of the pH and APFO concentration of the BGE and the capillary temperature were studied in order to achieve optimized enantioseparation. Optimization of CE-MS parameters, such as sheath-liquid composition and flow rate, ESI and MS settings was performed in order to prevent analyte fragmentation and achieve sensitive detection. Selective detection and quantification of 14 chiral proteinogenic AAs was achieved with chiral resolution between 1.2 and 8.6, and limits of detection ranging from 130 to 630 nM injected concentration. Aspartic acid and glutamic acid were detected, but not enantioseparated. The optimized method was applied to the analysis of chiral AAs in cerebrospinal fluid (CSF). Good linearity (R(2) > 0.99) and acceptable peak area and electrophoretic mobility repeatability (RSDs below 21% and 2.4%, respectively) were achieved for the chiral proteinogenic AAs, with sensitivity and chiral resolution mostly similar to obtained for standard solutions. Next to l-AAs, endogenous levels of d-serine and d-glutamine could be measured in CSF revealing enantiomeric ratios of 4.8%-8.0% and 0.34%-0.74%, respectively, and indicating the method's potential for the analysis of low concentrations of d-AAs in presence of abundant l-AAs. [less ▲]

Protamines are a group of highly basic peptides that are sometimes added to insulin formulations to prolong the pharmacological action. In this study, different methods were investigated to identify ... [more ▼]

Protamines are a group of highly basic peptides that are sometimes added to insulin formulations to prolong the pharmacological action. In this study, different methods were investigated to identify protamine in insulin formulations. Capillary electrophoresis in aqueous and non-aqueous media was tested to separate these peptides with very close amino acid sequences. Different buffers (phosphate or formate, both acidified) and various additives (principally negatively charged and neutral surfactants) were investigated to optimize peptide separation. Finally, a micellar electrokinetic capillary chromatography method using a capillary of 120 cm effective length and an aqueous background electrolyte made up of 100 mM phosphate buffer (pH 2) and 50 mM Thesit(R) gave the best results, providing the separation of the four major protamine peptides within 25 min. [less ▲]

A LC method using a chiral stationary phase (CSP) with cellulose tris(3-chloro-4-methylphenylcarbamate) as chiral selector in polar organic mode (POM) was developed for the separation of the ... [more ▼]

A LC method using a chiral stationary phase (CSP) with cellulose tris(3-chloro-4-methylphenylcarbamate) as chiral selector in polar organic mode (POM) was developed for the separation of the biopharmaceutic classification system (BCS) class II chiral prodrug eslicarbazepine acetate (ESL) and its main metabolites, namely eslicarbazepine, its optical antipode, (R)-licarbazepine, and the achiral oxcarbazepine (OXC). The percentage of methanol (MeOH) in the mobile phase containing acetonitrile (ACN) as the main solvent was found to significantly influence analyte retention and resolution. A reversal of elution order of OXC and (R)-licarbazepine was observed, depending on the MeOH percentage in the mobile phase. The optimized mobile phase consisted of ACN/MeOH/acetic acid/diethylamine (95/5/0.2/0.07; v/v/v/v). The potential of this chemo- and enantioselective LC method combined with solid-phase extraction (SPE) was then evaluated for in vitro metabolism studies using ESL as a model case. Only eslicarbazepine could be detected after incubation of ESL in human liver microsome systems. [less ▲]